Growth and mortality of Pinctada imbricata (Mollusca: Pteridae) in Guamachito, Araya Peninsula, Sucre State, Venezuela

Abstract

Growth, size distribution and mortality of Pinctada imbricata from Guamachito, Araya Peninsula, Venezuela, were analyzed between January and December 2000. Monthly samples were taken on perpendicular transepts to the coastline with an artisanal dredge, and data on sea surface temperature, dissolved oxygen and salinity were registered. The size distribution was variable, with a predominance of size between 50 and 70 mm in length, which represented 75% of the population. The greatest amount of juveniles was observed in March, when the mean length of the population was 55.8 mm. The variation in mean wet and dry weights presented a similar trend, with minimum values in June, July, September and October. The length/wet weight and length/ dry weight relationships were highly significant (P < 0.05). The parameters of the seasonal von Bertalanffy growth equation were L_∞ = 85.15 mm, K = 1.42 yr^–1, ts = 0.2 and C = 0.20, indicating a slow growth in the period from July to November (WP = 0.42) that could be associated with the environmental conditions of the area. Longevity was estimated to be three years. Total mortality rate (Z) was 3.45 per year for small individuals (10–36 mm) and 14.36 per year for the larger individuals (36–84 mm). The high growth rate of P. imbricata supports its use for aquacultural purposes in the region. The Guamachito oyster bank shows good conditions to support sustained fishery exploitation, considering fishery parameters such as registered catch, optimal effort, minimum extraction size, fishing mortality and natural mortality.